The present invention relates to the manufacture of a long elongate composite element, comprising long reinforcement fibers, embedded in a matrix of cured resin.
It is becoming more and more common to use composite materials for manufacturing structural components or load-bearing components or reinforcement elements, owing to the ever better performance which may be achieved with composite materials. Composite materials often allow considerable weight savings to be made while achieving equivalent mechanical performance. Moreover, in applications where the composite material is subject to considerable stress, it is very important to be able to benefit fully from the reinforcing action of the fibers. This requires absolute mastery of the manufacture of composite elements.
The role of the resin is to connect the fibers firmly to one another and to transmit stresses to the fibers. It is very important for the fibers to be totally impregnated and distributed homogeneously and in accordance with the desired level of reinforcement over the entire cross section of the composite element.
One of the known methods of manufacturing composite components with good mechanical qualities is known as “pultrusion”. This entails continuously unwinding the reinforcing fibers and dipping them in a resin bath to ensure that the fibers are impregnated with the resin. Then, all the fibers and impregnating resin are drawn through a heated die, in order to effect at least partial polymerization of the resin. In this way, it is possible continuously to draw products with a cross section dictated by the shape of the die. Unfortunately, pultrusion does not readily lend itself to high speed operation, as impregnation tends to be slow and difficult. Furthermore, the kinetics of the heat transfer phenomenon considerably limits the rate of manufacture.
Another known possibility consists in disposing the reinforcement fibers as desired in a mold, producing a vacuum and finally impregnating the fibers with the resin. The vacuum allows very effective impregnation. This method lends itself well to the manufacture of components of moderate finite dimensions, as a mold is used which corresponds to the shape and dimensions of the manufactured component. However, when it comes to the continuous manufacture of long components, it is not easy to impregnate the fibers correctly. And the more it is wished to accelerate production rates the more difficult it becomes to ensure perfect impregnation of the fibers with the resin.
Furthermore, the increasing commercial popularity of composite materials also depends on their cost price. It is therefore very important to be able to propose technological means capable of high manufacturing rates under the most competitive economic conditions possible.